It is usual when preparing a patient for surgery to treat an area surrounding the intended site of an incision by applying a biocide such as iodine or chlorhexidine to the skin surface. This is usually applied immediately preoperatively. After treatment, the area is covered with a sterile sheet or drape leaving an opening through which the surgeon can make an incision and perform an operation. The purpose of this procedure is to kill any colonies of micro-organism which exist on the patient's skin and which may access the surgical site giving rise to infection of the surgical wound. Although this procedure is largely effective in reducing the occurrence of post operative infection, a high proportion of cases in which infection does occur are attributed to autologous infection. Such infection if it does occur may have serious, or even fatal, consequences.
It is the practice in some hospitals as an added precaution to ask patients to wash themselves, or at least the areas intended for surgery, with an antiseptic soap once a day for one or two days prior to surgery. This wash is usually done under the shower and is thought to reduce the bacterial load on the patient's skin, and to remove micro-organisms from a wider area of skin than is practical in the operating theatre prior an operation.
The above treatments have in common that they are only effective against “transient” micro-organisms. “Transient” micro-organisms are those that exist on the surface of skin. The efficacy of such treatments against transient micro-organisms is discussed by Paulson, D. S. (American Journal of infection Control (1993), 21, 205-209) in respect of 4% chlorhexidine gluconate shower baths and Byrne, D. J. et al (J. Hospital Infection (1990), 15, 183-187) in respect of 4% chlorhexidine detergent. Garibaldi, R. A. (J. Hospital infection (1988), 11, Sup B 5-9) showed that 4% chlorhexidine gluconate was more effective than povidone iodine or triclocarban medicated soap for treating skin surface colonization. Nevertheless the frequency of intra-operative wound cultures was at best 4%, i.e. surface cultures were found on 4 patients in 100 intra-operatively.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
The present inventor has observed that while a patient's skin is treated pre-operatively with a biocide effective against “transient” micro-organism populations, surgeons are obliged to “scrub up” and this “surgical scrubbing” involves intensive scrubbing treatment with biocides and surfactants extending over several minutes under running water according to complex set down protocols. These scrubbing protocols are intended not only to remove “transient” organisms from the surface of the surgeon's hands, but also to kill “resident” micro-organisms which may reside within pores of the skin. The epidermis which is the outer layer of skin consists of five stratum, of which the stratum corneum is the outermost. Some micro-organisms may reside sub corneum, particularly but not only in sweat glands, hair follicles, and subcutaneous glands. Such “resident” micro-organisms are difficult to kill even with scrubbing and studies have shown that their removal is only partially accomplished by surgical scrubbing. It would be impracticable to scrub patients under running water to the same extent prior to surgery and doing so would only be partially effective
The commonly used preoperative compositions result in approximately a reduction of 2 log in “transient” micro-organisms on dry areas of skin, a reduction of 3 log on moist areas of skin (when measured in-vivo on hands and wrists using the “glove juice method” and when measured on fingertips using the “European method”), and have substantially no effect on the population of “resident” micro-organisms in the skin. The occurrence of “resident” micro-organisms varies greatly from one person to another and variations of up to ten fold in resident micro-organism counts can be found in a representative sample of a population. Since the normal preoperative treatment is relatively effective against “transient” micro-organisms, this implies that “resident” micro-organisms may play a role in autologous infection.
Neilsen et al. (J. Clinical Pat., (1975), 28, 793-797) examined the effect of 0.5% chlorhexidine in 62% ethyl alcohol on both superficial “transient” and “resident” flora. They concluded that a two step process including a pre-treatment with a detergent was essential for treating “resident” flora. Of fourteen volunteers examined, sub-corneum aerobic micro-organisms were found in each prior to treatment and remained in at least one case subsequent to the preferred treatment—i.e. a failure rate of 7%. The authors could only conclude that the treatment must be said “to eliminate to a high degree” the patients skin as a source of anaerobic and aerobic operation wound bacteria. Regretfully the intervening 30 years have shown even that conclusion to be unrealistically optimistic and the problem remains.
PCT/US98/06779 describes a method for preoperative skin preparation involving iodine and ethyl alcohol in a gel. Although the specification notes that micro-organisms may be “transient’ or “resident’, it contains no data or claim as to efficacy in respect of “resident” micro-organisms. Although primarily directed to an iodine based composition, the method disclosed (page 26) involves application of the gel to the surgical site immediately preoperatively with scrubbing for about 30 seconds. Both the composition and method differ from that herein disclosed.
It is also critically important to note that in the cited examples the primary biocides are chlorhexidine or iodine and with those biocides little, if any, subcutaneous penetration is possible because of the strong interactions between these biocidal actives and all body proteins. In the case of chlorhexidine these interactions cause the biocide to become attached (substantive) to the protein and in the case of iodine cause it to be deactivated by the protein. Therefore any subcutaneous action is dependant upon the ethanol contained therein.
This penetrating ethanol is quickly dissipated within the body and therefore there is no residual biocidal activity sub corneum beyond a few minutes. Recolonisation of these areas begins immediately after alcohol dissipation. Most surgical procedures take between 15 minutes and six hours.
Because of the currently perceived risk of post operative infection (including autologous infection) surgeons today routinely prescribe preoperative antibiotics as a prophylactic measure. This practice risks increasing the resistance of micro-organisms to antibiotics and is a major medical and social concern.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art. It is an object of preferred embodiments of the invention to provide improved methods of preparing a patient for surgery and compositions for use in that method which in highly preferred embodiments are more effective at reducing post operative infection than one or more prior art methods.